Non-volatile memory devices are in general memory devices that retain, or store, data even when not powered. Presently, non-volatile memory devices are utilized in a wide range of applications including, for example, mobile phones, digital cameras, memory cards, smart cards, and other applications where power is not always available, power is frequently interrupted, or lower power usage is required. Typical non-volatile memory devices include, for example, EPROM (Erasable and Programmable Read Only Memory) devices, EEPROM (Electrically Erasable and Programmable Read Only Memory) devices and flash memory. Split gate memory devices offer a solution which is low cost, re-programmable in system, and highly reliable. Split gate memory device is fabricated and integrated together with other types of devices, such as logic and high voltage (HV) devices, to form embedded memory.
A typical split gate embedded memory technology uses three polysilicon layers (also referred to as poly layers): one for floating gate, one for logic, HV and stack gate, and one for access (split) gate. However, there tend to be a few problems associated with conventional manufacturing method of embedded split gate memory technology. Firstly, during the manufacturing process, the oxide-nitride-oxide (ONO) interpoly layer may be exposed to many logic well photolithography steps. Secondly, complicated processes are required to provide protection for non-volatile memory (NVM) stack and HV devices. Thirdly, the manufacturing process may be unstable and thus results in less-than-ideal yield rate. For example, the profile of select gate of the split gate memory device is sensitive to pattern density which may vary from production to production. Tool situation may vary from run to run while wafer location (wafer to wafer) may also vary.
Accordingly, there remains a need for split gate embedded memory technology that addresses the aforementioned issues, and a manufacturing method thereof.